This article first describes Jacques Mehler's initial efforts to make psycholinguistics and, more generally, the cognitive sciences better known during his first years in Paris. Two lines of research on sentence perception, that we conducted in collaboration with Jacques, are then presented to illustrate his focus. In the Seventies, sentence perception was a central topic in psycholinguistics, with contrasting proposals of syntactic autonomy and interactivity being confronted. A first series of experiments aimed at defining the role of syntax in lexical selection process as revealed by the rapid serial visual presentation (RSVP) of the words in a sentence. The second series, using the phoneme monitoring technique, examined the clause as a processing unit during the auditory perception of sentences. These results confirm the fundamental role played by syntax in language processing.